Shadow tuning indicator



April 16, 1935. u. 1.. SMITH SHADOW TUNING INDICATOR Filed Oct. 31-, 193C) Fly.

INVENTOR Ue/. L. 5/)? 'f/? WITNESSES; m/fi v 0 D M ATT NEY Patented Apr. 16, 1935 PATENT-OFFICE SHADOW TUNING INDICATOR "Ue'l LQSmith, Montville, N. J., assignor to Westinghouse Electric & Manufacturing Company,

East Pittsburgh, Pa., sylvania a corporation of Penn- Application October 31, 1933, Serial No. 696,046

7 Claims.

casting station. n

As is generally understood the tonequali-ty of reproduction of a radio receiving set is greatly influenced by the accuracy with which the set is tuned to the'carrier. wave received.;. With the advent of automatic volume control in broadcast receivers, the volume remains quite uniform as a set is tuned over a carrier wave, and it has become increasingly difficult for the operator of a radio set to ascertain whenit is properly tuned. Hence, an operator, whoseear for tone is deficient, may tune a set in such a manner that the tonequal-ity of its reproduction is very-badly distorted, to the great annoyance .of others.

In previous attempts to remedy this difficulty a measuring device, such a conventional milliammetenhas been commonly mounted on the receiver and connectedinto the plate circuit of the radio or the intermediate frequency amplifier tubes. .By carefully observing such an instrument, it is possible, to accurately determine the proper condition of resonance. But such indicators were unsatisfactory with the general public because of the average persons inability of, or aversion to, tak- .ing sufiicient care to read a scientific measuring instrument while tuning the radio set. Consequently, such tuning indicators have not been generally effective in assuring the proper tuning of radio broadcast receivers.

It is accordingly an object ofmy invention to provide an improved radio tuningin'dicator which Willfgivea readily observable indication.

It is a further object of my invention to provide an illuminated radio tuning indicator which will present contrasting indications.

Another object of my invention is to provide a radio tuning shadow indicator in combination with the usual station selector for simultaneous observation.

In accordance with my invention, the tuning indicator is provided in combination with the pilot lamp which, in a certain type of rado set, is mounted adjacent to or within the station selector drum. In this embodiment, the tuning indication is given by the movements of a perforated shutter which is pivotally mounted within the drum between the pilot lamp and the window through which the drum is observed. The aperture in the shutter vane is of such shape and size that in one position it will pass a beam of light which is wide enough to illuminate the entire window. As the set is tuned to acarrier wave, the shutter is rotated in accordance with tuning of the set to resonance with the received signal, and the beam of light projected on the window is restricted toa narrow band of light across the middle of the window. Hence, the pilot. lamp simultaneously serves two purposes, and it is unnecessary for the operator to watch two windows or screens, while he tunes the radio set.- The operator merely 10 watches the window of the tuning drum and simultaneously observes the position ofthe tuning member and the resonance condition of the set. The invention itself, however, both as to its organization and its method of operation, to- 15 gether with additional objects and advantages thereof, will best be understood from the following description of specific embodiments, when read in conjunction with the accompanying drawing, in which: 1 I

Figure 1 is a side'elevational View partly in section showing the installation of my tuning indicator in a conventional, radio receiving set; Fig. 2 is a detail view showing the apertured shutter which varies the width. of the band of light on the station selector drum in accordance with the tuning of the radio receiver to resonance with a received signal; and

Fig. 3 is an elevational view showing the combined station selector and resonance indications as they appear onthe tuning dial.

Referring more specifically to Fig. 1 .of the drawing, a conventional radio receiving set II is shown comprising a station selector drum I2 having a pilot lamp l3 mounted therein. The selector drum isturned by manipulating the knob l5, and a tuning member, such as a variablecondenser I6, .is thereby adjustedto various selected positions, as indicated by a; suitable scale. I'I provided on the periphery of the drum. The surface of the drum, which is of translucent material, is illuminated from within by the pilot lamp I3, and the illuminated scale I! is viewed through a window It in a dial plate IS on the front of the set.

In order that the illuminated indications viewed at the window 18 may also serve to in- .dicate the resonance condition of the set to the received signals, an electro-responsive meter movement 23 is mounted in a suitable open ended enclosure 24 within the tuning drum l2 where it pivotally supports a shutter 25 between the pilot lamp [3 and the illuminated window I8. For clearness of illustration a DArsonval type of meter movement is represented, but any other suitable meter movement may be used. The coil 21 of the movement 23 is connected in any suitable manner, as in the plate circuit of the detector tube or the intermediate amplifier tubes whereby it will be energized in accordance with the tuning of the set to the received signals. The shutter 25 is provided with an aperture 26 through which the light may pass, as shown in Fig. 2. The edges of the shutter 25 are bent angularly to cast marginal shadows upon the drum along the upper and lower edges of the window.

The shutter is so mounted that when the electro-responsive device receives its maximum energization, it is turned at right angles to the light beam and passes a wide band of light to the window. As the set is tuned directly upon a carrier wave the energization of the device is decreased and the shutter 25 is turned so that its opaque edge portions cast wider marginal shadows which narrow the beam of light projected through the shutter aperture 26 upon the window. As the band of light is narrowed, the indication presented at the window I8 is similar to that represented in Fig. 3. Hence, as the operator is adjusting the selector drum I 2 and observing its position through the window '18, he also simultaneously receives a visual manifestation which shows him when the set is tuned exactly on the carrier wave.

It will be apparent that I have provided a radio tuning intensity indicator which may be mounted and observed in combination with the usual station selector, and which is so simple in operation that it does not require precise reading and observation and does not add appreciably to the complication of tuning a radio set.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. The combination with a radio receiving set including a pilot lamp and a. station selector scale illuminated thereby, of a tuning indicator comprising means responsive to the tuning of the set to resonance with a received signal for varying the area of said selector scale illuminated by said pilot lamp.

2. The combination with a radio receiving set including a pilot lamp and a translucent station selector scale illuminated thereby, of a tuning indicator comprising an apertured shutter, means for pivotally supporting said shutter between said pilot lamp and said translucent scale, and means for rotating said shutter in accordance with the tuning of the set to resonance with a received signal.

3. The combination with a radio receiving set including a pilot lamp and a translucent station selector scale illuminated thereby, of a tuning indicator comprising electromagnetic means energized in accordance with the tuning of the set to resonance with the signal received and optical means actuated thereby for varying the area of the translucent scale illuminated by said pilot lamp.

4. The combination with a radio receiving set having a pilot lamp, and a translucent station selector scale illuminated thereby, of a tuning indicator comprising a shutter of opaque material, means for pivotally supporting said shutter between said pilot lamp and said translucent scale, said shutter having an apertured portion and angularly turned edges, means connected to said shutter for rotating the same comprising an electrornagnetic device energized from said set in accordance with the tuning thereof to resonance with a received signal.

5. In combination, a plate having a window aperture therein, a translucent graduated member adjacent said window, a lamp spaced from said member for illuminating the same, an apertured shutter, means for pivotally mounting said shutter between said lamp and said member for casting marginal shadows along opposite edges of the portion 01' the illuminated member viewed through said window, and means for moving said shutter to widen the marginal shadows and narrow said illuminated portion.

-6. In an indicating device the combination of approximate indicating means comprising a lamp, a graduated member illuminated thereby, and a stationary member adjacent thereto, and precise indicating means comprising a movable light controlling member for varying the illuminated area of said graduated member adjacent to said stationary member.

7. In combination, a drum having a translucent graduated periphery, means for pivotally supporting said drum on a horizontal axis, a lamp within said drum for illuminating the same, a stationary member adjacent to the periphery of said drum, an apertured shutter, means for pivotally supporting said shutter between said lamp and the periphery of the drum on a horizontal axis parallel to the axis oi. the drum, whereby a band of light is projected through the shutter onto the translucent periphery of the drum adjacent to said stationary member, and means for rotating said shutter to restrict the illuminated area of the drum.

UEL L. SMITH. 

